Photocatalyst comprising bimetallic nanoparticles and graphene oxide for denitrification reaction, and water treatment method using same

Abstract

Proposed are a photocatalyst, including titanium dioxide particles including titanium dioxide (TiO 2 ), a carbon material located on all or part of the surface of the titanium dioxide particles and including at least one selected from the group consisting of graphene, reduced graphene oxide (rGO), and carbon nanotubes (CNTs), and bimetallic nanoparticles supported on the carbon material and including first metal nanoparticles and second metal nanoparticles, and a water treatment method using the same. In the photocatalyst and the water treatment method using the same, the photocatalyst including bimetallic nanoparticles and graphene oxide is prepared, thereby exhibiting high reduction efficiency and high selectivity to nitrogen gas even without the use of an external electron donor.

What is claimed is: 
     
       1. A photocatalyst, comprising:
 titanium dioxide particles comprising titanium dioxide (TiO 2 ); 
 a carbon material located on all or part of a surface of the titanium dioxide particles and comprising reduced graphene oxide (rGO); and 
 bimetallic nanoparticles supported on the carbon material and comprising first metal nanoparticles and second metal nanoparticles, 
 wherein the first metal nanoparticles comprise copper (Cu) and the second metal nanoparticles comprise palladium (Pd), and 
 wherein both the first metal nanoparticles and the second metal nanoparticles have (111) facet. 
 
     
     
       2. The photocatalyst of  claim 1 , wherein the photocatalyst is a denitrification catalyst for removing a nitrate ion (NO 3   − ). 
     
     
       3. The photocatalyst of  claim 1 , wherein a denitrification reaction is carried out without addition of an electron donor using the photocatalyst. 
     
     
       4. The photocatalyst of  claim 3 , wherein nitrogen gas (N 2 ) is produced as a final product through the denitrification reaction using the photocatalyst. 
     
     
       5. The photocatalyst of  claim 1 , wherein an average size of the first metal nanoparticles is 1 to 5 nm, and an average size of the second metal nanoparticles is 1 to 5 nm. 
     
     
       6. The photocatalyst of  claim 1 , wherein the bimetallic nanoparticles comprise the first metal nanoparticles (M1) and the second metal nanoparticles (M2) at a mass ratio (M1:M2) of 3:7 to 7:3. 
     
     
       7. The photocatalyst of  claim 6 , wherein the bimetallic nanoparticles comprise the first metal nanoparticles (M1) and the second metal nanoparticles (M2) at a mass ratio (M1:M2) of 4:6 to 6:4. 
     
     
       8. The photocatalyst of  claim 1 , comprising:
 100 parts by weight of the titanium dioxide (TiO 2 ) particles; 
 0.1 to 5 parts by weight of the carbon material; and 
 0.2 to 10 parts by weight of the bimetallic nanoparticles. 
 
     
     
       9. A water treatment method comprising carrying out a denitrification reaction for reducing a nitrate ion (NO 3   − ) into nitrogen gas (N 2 ) by decomposing water using the photocatalyst of  claim 1  as a catalyst under light irradiation. 
     
     
       10. The water treatment method of  claim 9 , wherein the denitrification reaction is carried out at a pH of 3 to 10. 
     
     
       11. The water treatment method of  claim 9 , wherein the light irradiation is performed using light comprising ultraviolet rays or visible light rays. 
     
     
       12. The water treatment method of  claim 9 , wherein the light irradiation is performed using light having a wavelength of 270 to 450 nm. 
     
     
       13. The water treatment method of  claim 9 , wherein the denitrification reaction is carried out without use of an external electron donor. 
     
     
       14. A method of preparing the photocatalyst of  claim 1 , comprising:
 (a) preparing a first mixed solution comprising titanium dioxide (TiO 2 ) particles and a carbon material comprising reduced graphene oxide (rGO); 
 (b) preparing a composite comprising the titanium dioxide particles and the carbon material located on all or part of a surface of the titanium dioxide particles by stirring and drying the first mixed solution; 
 (c) preparing a second mixed solution comprising the composite, a first metal nanoparticle precursor and a second metal nanoparticle precursor; and 
 (d) preparing a photocatalyst comprising first metal nanoparticles and second metal nanoparticles supported on the carbon material of the composite by irradiating the second mixed solution with light, wherein the first metal nanoparticles comprise copper (Cu) and the second metal nanoparticles comprise palladium (Pd). 
 
     
     
       15. The method of  claim 14 , wherein the method further comprises (a′) preparing the reduced graphene oxide by reducing graphene oxide, before step (a). 
     
     
       16. The method of  claim 14 , wherein in step (c), the first metal nanoparticle precursor comprises at least one selected from the group consisting of copper (II) chloride (CuCl 2 ), copper (II) acetate (Cu(CH 3 COO) 2 ), and copper (II) nitrate (Cu(NO 3 ) 2 ). 
     
     
       17. The method of  claim 14 , wherein in step (c), the second metal nanoparticle precursor comprises at least one selected from the group consisting of palladium (II) chloride (PdCl 2 ), palladium (II) acetate (Pd(CH 3 COO) 2 ), and palladium (II) nitrate (Pd(NO 3 ) 2 ). 
     
     
       18. The method of  claim 14 , wherein step (d) is performed through photodeposition.